Previously in the use of over the spindle adaptors for quick change tool holders such as set forth in the co-pending application there was employed a retractible spring biased sleeve mounted upon a body on a spindle having an internal taper engaging a series of balls mounted within the body extending from its opposite sides for operative retaining engagement with a tapered collar on the tool holder for operatively retaining the tool holder within and upon the spindle. In working with aluminum parts, the cuttings often got into and piled up within the ball assemblies and related parts.
With increased usage of aluminum castings and the boring into such castings with certain types of multiple spindle tools, the tools employed are approximately one-third the length of the tools previously used on multiple spindle drill heads or on single spindle applications.
There is a need for an improved quick change spindle adaptor wherein ball bearings are not needed to effectively anchor the tool holder within and upon the spindle and to axially bias the tool holder and the tool mounted thereon into the spindle.